1. Field of Invention
This invention relates to novel retinoic acid analogs that have substitutions at C-4 (hereafter referred to as C-4 substituted retinoic acid analogs except otherwise stated). This invention also relates to methods of synthesis of these novel C-4 substituted retinoic acid analogs and methods of using these novel C-4 substituted retinoic acid analogs as therapeutic agents for cancers and dermatological diseases and conditions. This invention also relates to pharmaceutical compositions containing these novel C-4 substituted retinoic acid analogs.
Preferably, the novel C-4 retinoic acid analogs are all-trans retinoic acid (ATRA) and 13-cis retinoic acid (13-CRA) analogs.
2. Description of the Related Art
All-trans retinoic acid (ATRA), the biologically most active metabolite of vitamin A, plays a major role in cellular differentiation and proliferation of epithelial tissues. Differentiating agents, such as ATRA, redirect cells towards their normal phenotype and therefore may reverse or suppress evolving malignant lesions or prevent cancer invasion (Hill D L and Grubbs C J, Retinoids and cancer prevention, Annu Rev Nutr 12: 161-181, 1992; Hong W K and Itri L, Retinoids and human cancer, In The Retinoids: Biology, Chemistry and Medicine, Sporn M B, Roberts A B and Goodman D S (eds), pp 597-630, Raven Press: New York, 1994). However, the therapeutic effects of ATRA are undermined by its rapid in vivo catabolism by cytochrome P450-dependent enzymes (Muindi J, Frankel S R, Miller W H Jr, Jakubowski A, Scheinberg D A, Young C W, Dmitrovsky E and Warrell R P Jr, Continuous treatment with all-trans retinoic acid causes a progressive reduction in plasma drug concentrations: implications for relapse and retenoid “resistance” in patients with acute promylocytic leukemia, Blood 79: 299-303, 1992; Smith M A, Parkinson D R, Cheson B D and Friedman M A, Retinoids in cancer chemotherapy, J Clin Oncol 10: 839-864, 1992; Warrell R P Jr., Differentiating agents, In Cancer, principles and practice of oncology; DeVita Jr, Hellman S and Rosenberg S A (eds), Vol. I, pp 483-490, Lippincott: Philadelphia, 1997; Kizaki et al., 1996).
In addition, ATRA is known to have therapeutic effects for many dermatological diseases. Again, the fast catabolism of ATRA has limited the usefulness of the compound for treatment. (Cunliffe, 1986; Griffiths CEM, Fischer G J, Finkel L J, Voorhees J J, Mechanism of action of retinoic acid in skin repair, BR Journal of Dermatology, 127 (Suppll):21-24, 1992).
ATRA can be metabolized through several routes. The physiologically most prominent pathway starts with hydroxylation at the 4-position of the cyclohexenyl ring, leading to the formation of 4-hydroxy-ATRA that is converted to more polar metabolites via 4-oxo-ATRA (Frolik C A, Roberts A B, Tavela T E, Roller P P, Newton D L and Sporn M B, Isolation and identification of 4-hydroxy-and 4-oxo-retinoic acid, In vitro metabolites of all-trans-retinoic acid in hamster trachea and liver, Biochemistry 18: 2092-2097, 1979; Frolik C A, Roller P P, Roberts A B and Sporn M B, In vitro and in vivo metabolism of all-trans-and 13-cis-retinoic acid in hamsters, J Biol chem 255: 8057-8062, 1980; Roberts A B, Nichols M D, Newton D L and Sporn M B, In vitro metabolism of retinoic acid in hamster intestine and liver, J Biol Chem 254: 6296-6302, 1979; Roberts A B, Lamb L C and Sporn M B, Metabolism of all-trans-retinoic acid in Hamster liver microsomes: oxidation of 4-hydroxy-to 4-keto-retinoic acid, Arch Biochem Biophys 199: 374-383, 1980; Van Wauwe J, Coene M-C, Cools W, Goosens J, Lauwers W, Le Jeune L, van Hove C and van Nyen G, Liarozole-fumarate inhibits the metabolism of 4-keto-all-trans-retinoic acid, Biochem Pharmacol 47: 737-741j, 1994; Napoli J L, Retinoic acid biosynthesis and metabolism, FASEB J 10: 993-1001, 1996). The first and third catabolic steps are catalyzed by a cytochrome P450-dependent enzyme complex (Frolik C A, Roller P P, Roberts A B and Sporn M B, In vitro and in vivo metabolism of all-trans-and 13-cis-retinoic acid in hamsters, J Biol chem 255: 8057-8062, 1980; Leo M A, Lida S and Lieber C S, Retinoic acid metabolism by a system reconstituted with cytochrome P450, Arch Biochem Biophys 243: 305-312, 1984; Van Heusden J, Wouters W, Ramackers F C S, Krekels M D W G, Dillen L, Borgers M and Smets G, All-trans-retinoic acid metabolites significantly inhibit the proliferation of MCF-7 human breast cancer cells in vitro, Br J Cancer 77: 26-32, 1998a; Van Heusden J, Wouters W, Ramackers F C S, Krekels M D W G, Dillen L, Borgers M and Smets G, All-trans-retinoic acid metabolites significantly inhibit the proliferation of MCF-7 human breast cancer cells in vitro, Br J Cancer 77: 1229-1235, 1998b). Although the exact nature of this enzyme remains to be elucidated, a cytochrome P450 enzyme (designated CYP26) with specific ATRA 4-hydroxylase activity, which is also rapidly induced by ATRA has recently been cloned from zebra fish, mouse and man (for reviews, see Haque M, Andreola F, DeLuca L M, The cloning and characterization of a novel cytochrome P450 family, CYP26, with specificity towards retinoic acid, Nutri Rev 56:84-85, 1999; Sonneveld E and Vander Sagg P T, Metabolism of retinoic acid: implications for development and cancer, Inter. J Vit Nutr Res 68: 404-410, 1998).
Initially, the 4-hydroxylase activity was thought to mainly reside in the liver (Roberts A B, Lamb L C and Sporn M B, Metabolism of all-trans-retinoic acid in Hamster liver microsomes: oxidation of 4-hydroxy-to 4-keto-retinoic acid, Arch Biochem Biophys 199: 374-383, 1980), but its presence has now been demonstrated in skin and tumor cells and tissues (Vanden Bossche H, Willemsens G, Retinoic acid and cytochrome P450, In Retinoids: 10 Years On. Saurat J H (ed). pp 79-88, Karger: Basel, 1990; Varani J, Gendimenico G A, Hhah B, Gibbs D, Capetola R J, Mezick J A and Voorhess J J, A direct comparison of pharmacologic effects of retinoids on skin cells in vitro and in vivo, Skin Pharmacol 4: 254-261, 1991; Wouters W, Van Dun J, Dillen A, Coene M. C, Cools W and De Coster R, Effects of liarozole, a new antitumoral compound an retinoic acid-induced inhibition of cell growth and on retinoic acid metabolism in MCF-7 breast cancer cells, Cancer Res 52: 2841-2846, 1992; Krekels M D W G, Zimmerman J, Janssen B, Van Ginckel R, Van Hove C, Coene M.-C and Wouter W, Analysis of the oxidative catabolism of retinoic acid in rat Dunning R 3327G prostate tumors, Prostate 29: 36-41, 1996).
In principle, inhibitors of 4-hydroxylase should increase endogenous levels of ATRA (acting as ‘ATRA-mimetics’) and overcome some ATRA-resistance. A number of azole compounds which inhibit several cytochrome P450 enzymes have also been shown to be inhibitors of ATRA 4-hydroxylase (Williams J B and Napoli J L, Metabolism of retinoic acid and retinol during differentiation of F9 embryonal cells, Proc Natl Acad Sci USA 82: 4658-4662, 1985; Williams J B and Napoli J L, Inhibition of retinoic acid metabolism by imidazole antimycotics in F9 embroynal carcinoma cells, Biochem Pharmacol 36: 1386-1388, 1987; Napoli J L, Retinoic acid biosynthesis and metabolism, FASEB J 10: 993-1001, 1996; Roberts A B, Nichols M D, Newton D L and Spom M B, In vitro metabolism of retinoic acid in hamster intestine and liver, J Biol Chem 254: 6296-6302, 1979; Vanden Bossche H, Willemsens G and Janssen P A J, Cytochrome-P-450-dependent metabolism of retinoic acid in rat skin microsomes: Inhibition by ketoconazole, Skin Pharmacology 1: 176-185, 1988; Van Wauwe J P, Coene M C, Goossens J, Van Nijen G, Cools W, Lauwers W, Ketoconazole inhibits the in vitro and in vivo metabolism of all-trans-retinoic acid, J Pharmacol Exp Ther, 245:718-722, 1988; Freyne E, Raeymaekers A, Venet M, Sanz G, Wouters W, De Coster R and Van Wauwe J, Synthesis of Liazal™, a retinoic acid metabolism blocking agent (RAMBA) with potential clinical applications in oncology and dermatology, Bioorg Med Chem Lett 8: 267-272, 1998). The discovery of retinoic acid metabolism blocking agents (RAMBAs) have led to interest of using RAMBAs in the treatments of cancers. (Miller, Jr., W. H., The Emerging Role of Retinoids and Retinoic Acid Metabolism Blocking Agents in the Treatment of Cancer, Cancer, 83, 1471-1482, 1998). Inhibitors of retinoic acid metabolism are known as retinoic acid metabolism blocking agents or “RAMBAs”.
Liarozole fumarate (LIAZAL™), a (1H-imidazol-1-ylmethyl)-1H-benzimidazole derivative, is one of the first new generation RAMBAs in clinical practice. Liarozole fumarate may soon be approved for the treatment of prostate cancer. (see, Waxman J. Roylance R., Editorial: New Drugs for Prostate Cancer? Eur. J. Cancer, 34, 437, 1998; and Debruyne, F. J. M. et al., Liarozole-A Novel Treatment Approach for Advanced Prostate Cancer: Results of a Large Randomized Trial versus Cyproterone, Urology, 52, 72-81, 1998)
Studies of liarozole's pharmacodynamics revealed that it inhibits ATRA 4-hydroxylase. (De Coster R, Wouters W, Van Ginckel R, End D, Krekels M, Coene M. -C and Bowden C, Experimental studies with liarozole (R75251): an antitumoral agent which inhibits retinoic acid breakdown, J Steroid Biochem Molec Biol 43: 197-201, 1992) However, the FDA's review of phase III trial data for liarozole in prostate cancer was negative. Although clinical efficacy was seen, the activity/toxicity ratio was considered insufficient. Hence Janssen Pharmaceutica NV, liarozole's manufacturer, has discontinued clinical development of liarozole (Wouters W (2000) Personal communication; Njar V C O and Brodie A M H, Inhibitors of cytochrome P450 enzymes: Their role in prostae cancer therapy, I Drugs 1: 495-506, 1999c). It appears that the reason for the high toxicity was that liarozole inhibits ATRA 4-hydroxylase only at micromolar concentrations, and at those levels it also exhibits harmful inhibitory activity with other cytochrome P450 enzymes (Bruynseels et al., 1990). The adverse side-effects of liarozole in the treatment of prostate cancer may be caused by a lack of selectivity for and/or potent inhibition of ATRA 4-hydroxylase enzyme.
Because of therapeutic benefits of liarozole for prostate cancer are limited by its side-effects, it would be useful to have compounds that inhibit ATRA 4-hydroxylase in nanomolar concentrations and have greater specificity for ATRA 4-hydroxylase than liarozole. Such compounds may avoid the harmful side-effects of liarozole and be tolerated better. Such compounds may also be useful in the treatment of other types of cancers and various dermatological conditions.
Thus, this invention helps overcome the problems of treating cancers and dermatological diseases and dermatological conditions with novel compounds that block catabolism of all-trans retinoic acid. These novel compounds have higher specificity to enzymes involved in retinoic acid catabolism and lower toxicity for the patient. Selective and potent inhibitory compounds of ATRA catabolism, using nanomolar concentration of the compounds, result in effective modulation to desirable levels of ATRA, either endogenous ATRA or of ATRA mimetic compounds. With higher levels of ATRA, the patient will have improved prognosis and outcomes.
The novel compounds in this invention are ATRA and 13-CRA analogs that have substitutions at the C-4.